A process for treating BOD, nitrogen and phosphorus containing wastewater, wherein the process includes the steps of providing wastewater influent into an anoxic zone having activated sludge and mixing the wastewater influent with the activated sludge in the anoxic zone to form a mixed liquor. The process further includes providing the mixed liquor into one more further treatment zones and transferring a portion of the mixed liquor from the further treatment zone to a membrane filter wherein a filtrate is separated from sludge. The process also includes selectively recycling at least a portion of the sludge to the anoxic zone as recycled activated sludge.